Since, for example, 1.alpha.,25-dihydroxycholecalciferol or 1.alpha.,24-dihydroxycholecalciferol is a substance that exhibits Ca regulatory action known to be a physiological action of vitamin D.sub.3, it is referred to as active vitamin D.sub.3. Although the physiological action of active vitamin D.sub.3 is diverse, probably regarding the differentiation inducing action and growth inhibitory action of active vitamin D.sub.3, findings have been obtained which state that the active vitamin D.sub.3 is effective against psoriasis which is a refractory skin disease, by a mechanism which normalizes the undifferentiation and accelerated growth of epidermal cells which are considered to be the cause of this disease (see T. Matsunaga, et al., J. Dermatol., Vol. 17, No. 3, p. 135 (1990)).
Since skin diseases such as psoriasis are diseases of the epidermal layer of the skin outer layer, local administration rather than systemic administration in the form of oral administration or injections and so forth is more advantageous in terms of bioavailability. Moreover, this type of administration is also preferable since it is possible to prevent systemic adverse side effects. Examples of drug forms for local administration include semi-solid preparations such as ointments and creams; liquid preparations such as lotions and liniments; tapes; poultices and powders. However, the semi-solid preparations or liquid preparations are preferred in consideration of the pathology of psoriasis.
Known examples of semi-solid preparations include an oily ointment having 1.alpha.,24-dihydroxyvitamin D.sub.3 for its primary drug and white Petrolatum for its base (Japanese Examined Patent Publication No. 3-68009), a cream preparation containing an oil phase component comprising a viscosity adjuster such as cetyl alcohol and a lipophilic solubilizer such as liquid paraffin, a surfactant such as sorbitan monostearate (span 60), and an aqueous phase component such as propylene glycol (Japanese Unexamined Patent Publication No. 4-210903), and an O/W emulsion ointment having 1.alpha.,24-dihydroxyvitamin D.sub.3 for its primary drug, and containing an oil phase component comprising a solid oil component such as white Petrolatum, a surfactant comprising sodium laurylsulfate, etc., and an aqueous phase component comprising propylene glycol, etc. (Japanese Examined Patent Publication No. 3-68009). In addition, an example of a known cream preparation has 1.alpha.,24-dihydroxyvitamin D.sub.3 for its primary drug, and contains a solid oil component comprising white Petrolatum, etc., an oil phase component containing a liquid oil component comprising squalane, etc., a surfactant such as polyoxyethylene hydrogenated castor oil 60, and an aqueous phase component such as propylene glycol (specification of WO95/6482).
However, when considering the pathology of skin diseases, lotion preparations are preferable as preparations for local administration. Since roughly 1/3 of the patients in which psoriasis occurs on the scalp in particular have the hair, lotions are preferable which do not become sticky at locations where there is (the) hair, are easily applied, and have the optimum viscosity for inhibiting running (having a viscosity of 500 to 1400 mPa.multidot.s when measured with a Brookfield rotational viscometer using a spindle no. LV4, at 60 rpm and 25.degree. C). In addition, it is desirable that this viscosity not be easily affected by external stimulation such as temperature or vibrations so that it remains constant at all times. Moreover, since the pathology of psoriasis involves an abnormality in which epidermal cells of the skin are destroyed, and since it is predicted that there is weak resistance to irritating substances, it is preferable that preparations used for psoriasis have a low level of irritation.
In general, lotions are roughly classified into solution-type lotions and emulsion-type lotions.
Of active vitamin D.sub.3 lotions, solution-type lotions of calcipotriol or 20(R)-22-oxa-vitamin D.sub.3 derivative are disclosed in the specification of WO91/12807 and the specification of WO92/01454. Since these lotions use a solvent such as ethanol giving a low viscosity to the lotion, not only do they run easily when applied preventing the preparation from effectively remaining at the affected area, but also when applied to the hairline on the forehead, there is a problem of the preparation getting into the eyes. In addition, there is also concern over the irritability of organic solvents such as ethanol used as solvent or absorption enhancer.
An example of a emulsion-type lotion is described, for example, in Japanese Unexamined Patent Publication No. 60-174705, and is composed of active vitamin D.sub.3 and its derivatives, an oil phase component such as spermaceti wax, cetanol, Petrolatum or squalane, a surfactant such as polyoxyethylene (10 mol) monostearate or sorbitan monooleate, and an aqueous phase component such as glycerin. In addition, an emulsion-type lotion is also disclosed in Japanese Examined Patent Publication No. 3-68009 that contains 1.alpha.,24-dihydroxyvitamin D.sub.3, an oil phase component comprising a solid oil component such as stearyl alcohol and a liquid oil component such as liquid paraffin, and a surfactant comprising sodium laurylsulfate.
If these emulsion-type lotions are, for example, stored in an environment of 50.degree. C. or lower or stimulated by vibration, a change in viscosity occurs and the gelation is observed.
Namely, conventional active vitamin D.sub.3 emulsion lotions are not always satisfactory with respect to the point of pharmacological activity and chemical stability of the primary drug, the point of having optimum viscosity with respect to, for example, not sticking to areas of (the) hair, being easily applied and not running easily, the point of feel during application, and the point of physical stability of the preparation when subjected to long-term storage, heat or vibrations etc.